Cancer, chemicals, Carson and smoking

Rachel Carson, in her hugely influential book Silent Spring, wrote that she expected an
epidemic of cancer caused by chemicals in the environment,
especially DDT, indeed she thought it had already begun in the
early 1960s:

``No longer are exposures to dangerous
chemicals occupational alone; they have entered the environment of
everyone-even of children as yet unborn. It is hardly surprising,
therefore, that we are now aware of an alarming increase in
malignant disease.

The increase itself is no mere matter
of subjective impressions. The monthly report of the Office of
Vital Statistics for July 1959 states that malignant growths,
including those of the lymphatic and blood-forming tissues,
accounted for 15 per cent of the deaths in 1958 compared with only
4 per cent in 1900. Judging by the present incidence of the
disease, the American Cancer Society estimates that 45,000,000
Americans now living will eventually develop cancer. This means
that malignant disease will strike two out of three families. The
situation with respect to children is even more deeply disturbing.
A quarter century ago, cancer in children was considered a medical
rarity. Today, more American school children die of cancer than
from any other disease. So serious has this situation become that
Boston has established the first hospital in the United States
devoted exclusively to the treatment of children with cancer.
Twelve per cent of all deaths in children between the ages of one
and fourteen are caused by cancer. Large numbers of malignant
tumors are discovered clinically in children under the age of five,
but it is an even grimmer fact that significant numbers of such
growths are present at or before birth. Dr. W. C. Hueper of the
National Cancer Institute, a foremost authority on environmental
cancer, has suggested that congenital cancers and cancers in
infants may be related to the action of cancer-producing agents to
which the mother has been exposed during pregnancy and which
penetrate the placenta to act on the rapidly developing fetal
tissues.''

Carson was wrong about this. Not only has DDT proved not to be a
carcinogen, but the cancer epidemic caused by exposure of the
general public to chemicals has wholly failed to materialise. Study
after study has found that there is no increase in cancer incidence
or death in the general population, when corrected for age, to be
explained by man-made chemicals. Those, like Paul Ehrlich, who
confidently predicted that the lifespan of Americans would fall to
42 years by the end of the twentieth century thanks to such cancer
epidemics, were proved badly wrong.

Here are the charts of cancer deaths for men and women, adjusted
for age, in the United States since the 1930s.

The one that stands out, of course, is lung cancer. The rapid
increase in lung cancer (boosted surely changing diagnosis in the
early years) was caused by the increase in smoking, of course.
Almost nobody now challenges that. But they did once. Indeed, one
of the most vociferous opponents of the theory that smoking causes
lung cancer was none other than Carson's mentor, William
Hueper.

So obsessed was Hueper with his notion that pesticides and other
synthetic chemicals were causing an epidemic of cancer and that
industry was covering this up, that he bitterly opposed the
suggestion that smoking take any blame - as an industry plot.

1. The total epidemiological, clinical,
pathological, and experimentalevidence on hand clearly indicates
that not a single but severalif not numerous industrial or
industry-related atmospheric pollutantsare to a great part
responsible for the causation of lung cancer.

2.While the available data do not permit any
definite statementas to the relative importance of the various
recognized respiratorycarcinogens in the production of lung cancers
in the generalpopulation, they nevertheless unmistakingly suggest
that cigarettesmoking is not a major factor in the causation of
lung cancernor had it a predominant role in the remarkable increase
ofthese tumors during recent decades.

3. In view of the fact thatnot only a great
deal of the existing circumstantial epidemiologicalevidence but
also pratically the entire factual and conclusiveevidence available
on exogenous respiratory carcinogens areeither of occupational
origin or point to industry-related factors,it would be most unwise
at this time to base future preventivemeasures of lung-cancer
hazards mainly on the cigarette theoryand to concentrate the
immediate epidemiological and experimentalefforts on this evidently
overpropagandized and insufficientlydocumented concept.

When environmentalists want to attack a sceptic these days, they
quite frequently accuse him or her of being the kind of person who
would have defended the tobacco lobby - in some cases with
justification. So it is ironic to find that possibly the most
iconic and original text of the entire environmental movement,
Silent Spring, was built on the work of a fervent tobacco defender.
Hueper is quoted frequently throughout Carson's book.

By the way, in my book I say that Rachel Carson `expected DDT
"to cause practically 100 per cent of the human population to be
wiped out from a cancer epidemic in one generation"'. This is
inaccurate: I slipped up. I relied on an article in a magazine called Front Page in
July 2003 for this quotation, and unusually I did not check it with
Carson's original text. Alerted by a reader, Ed Darrell (thanks!) I
have now checked Carson's Silent Spring, and while Carson strongly
implies that she does indeed expect a major mortality from cancer
caused by DDT, what she actually wrote is the following:

In the springof 1961 an
epidemic of liver cancer appeared among rainbowtrout
in many federal, state, and private hatcheries. Trout in both
eastern and western parts of the United States were affected; in
some areas practically 100 per cent of the trout over three years
of age developed cancer....The story of
the trout is important for many reasons, butchiefly
as an example of what can happen when a potent carcinogen is
introduced into the environment of any species. Dr. Hueper has
described this epidemic as a serious warning that greatly increased
attention must be given to controlling the number and variety of
environmental carcinogens. 'If such preventive measures are not
taken,' says Dr. Hueper, 'the stage will be set at a progressive
rate for the future occurrence of a similar disaster to the human
population.'

My book criticises Carson and her followers for their
exaggerated pessimism which led to the phasing out of DDT as an
anti-mosquito weapon and hence led directly to the resurgence of
malaria. This is a story that has been well told in many places and
deserves to be better known. But I find many of DDT's defenders
then go on to make a claim that I do not believe is correct, namely
that DDT had no impact on birds, and that the story that it led to
the thinning of eggshells in birds at the end of long food chains,
such as falcons and pelicans (and also damaged the reproduction of
predatory mammals such as otters), is false. I simply do not accept
that. The evidence of bioaccumulation in fat, of eggshell thinning
and of DDT's role in the decline of raptors and other predatory
birds in the 1960s seems to me fairly strong, though not overhwelming. The
ending of indiscriminate and widespread spraying of DDT is probably
a good thing.

It is, fortunately, very easy to use DDT against malarial
mosquitoes without poisoning birds. The solution is to use it
sparingly on the inside walls of houses, where anopheline
mosquitoes rest during the day. This targets the pest while not
allowing the pesticide to contaminate the food chain in nearby
ecosystems. The best of both worlds.

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